Yes he will, please try no to worry. It is a bit of a slog, but it does get better and the best thing you can do is stay calm. i got so cross sometimes, but its not their fault and not yours either!!!
You are doing the right thing, I went in first and said its nap/betime and lay her back down, but then after that, no interation. Sometimes it can take up to an hour to get them down. try not to let him cry, go in as soon as he's distressed and lay him back down, use PU/PD techniques, and leave the room everytime.
Does he know how to sit back down from standing and to lay himself down from sitting. These are far more diff skills than getting up in the firt place!! When you go in try to lay him dwon in the way he would get down himself and practice lots of sitting from standing and laying down when you're playing.
Hang in there!!! Kxxxx